Acetic acid is an important chemical raw material, which is mainly used to produce vinyl acetate, acetic anhydride, acetate and the like. Its global annual output is nearly 10 million tons. Currently, acetic acid is mainly industrial produced by methanol carbonylation routes, typically represented by Monsanto or Cativa™ processes, whose catalyst system is rhodium or iridium coordination compounds (Adv. Catal. 53, 2010, 1.). The defects of the two processes which need be further optimized to improve the economic efficiency are listed as follows: firstly, strongly corrosive HI exists in the catalyst recycle process, and thus the reactor must be made from the expensive anti corrosive materials; secondly, the existing industrial process uses homogeneous catalysts, and therefore there is a great energy cost for separation of the products and the catalyst; thirdly, the noble metal catalysts, such as rhodium catalyst or iridium catalyst, are very expensive; fourthly, the product acetic acid may contain trace amount of iodides which will severely affect the quality of acetic acid, to the disadvantage of the production of the acetic acid downstream products.
Fujimoto et al (Chem. Lett., 1984, 2047.) has discovered that methanol can generate acetic acid by a gas phase carbonylation on acidic molecular sieve catalyst. However, the catalyst stability and the selectivity for acetic acid are very low. The main reason is that at low temperature, the water generated from etherification of methanol will cause the passivation of the active centers in the molecular sieve; while at high temperature, methanol will be easily converted into carbon deposit and hydrocarbon. To prevent the impact of water, Iglesia et al have carried out a carbonylation reaction using dimethyl ether on molecular sieve catalyst to prepare methyl acetate (Angew. Chem. Int. Ed. 45, 2006, 1617.). In CN101613274A, a method of preparing methyl acetate by carbonylation of dimethyl ether has been disclosed, wherein a mordenite molecular sieve modified by pyridines organic amine is used as the catalyst. However, to obtain acetic acid, this method needs to be combined with processes of preparing dimethyl ether from methanol and hydrolysis of methyl acetate, affecting the economic efficiency.
In WO 2007/128955A1, a method of preparing carboxylic acid and/or its ester by carbonylation of alcohol and/or its derivatives with carbon monoxide has been disclosed, using silver loaded mordenite catalyst or H-typed mordenite catalyst. However, the catalyst stability is not ideal and the selectivity of acetic acid is not high.